/*
 * Created on 29-Mar-2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package org.gudy.azureus2.pluginsimpl.local.disk;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;

import org.gudy.azureus2.core3.config.COConfigurationManager;
import org.gudy.azureus2.core3.config.ParameterListener;
import org.gudy.azureus2.core3.disk.DiskManagerFileInfoListener;
import org.gudy.azureus2.core3.download.DownloadManager;
import org.gudy.azureus2.core3.download.DownloadManagerPeerListener;
import org.gudy.azureus2.core3.peer.PEPeer;
import org.gudy.azureus2.core3.peer.PEPeerManager;
import org.gudy.azureus2.core3.torrent.TOTorrent;
import org.gudy.azureus2.core3.torrent.TOTorrentFile;
import org.gudy.azureus2.core3.util.AESemaphore;
import org.gudy.azureus2.core3.util.Average;
import org.gudy.azureus2.core3.util.Debug;
import org.gudy.azureus2.core3.util.DirectByteBuffer;
import org.gudy.azureus2.core3.util.SystemTime;
import org.gudy.azureus2.plugins.disk.DiskManagerChannel;
import org.gudy.azureus2.plugins.disk.DiskManagerEvent;
import org.gudy.azureus2.plugins.disk.DiskManagerFileInfo;
import org.gudy.azureus2.plugins.disk.DiskManagerListener;
import org.gudy.azureus2.plugins.disk.DiskManagerRequest;
import org.gudy.azureus2.plugins.download.Download;
import org.gudy.azureus2.plugins.download.DownloadException;
import org.gudy.azureus2.plugins.utils.PooledByteBuffer;
import org.gudy.azureus2.pluginsimpl.local.download.DownloadImpl;
import org.gudy.azureus2.pluginsimpl.local.utils.PooledByteBufferImpl;

import com.aelitis.azureus.core.peermanager.piecepicker.PiecePicker;
import com.aelitis.azureus.core.peermanager.piecepicker.PieceRTAProvider;
import com.aelitis.azureus.core.util.CopyOnWriteList;

public class DiskManagerChannelImpl implements DiskManagerChannel, DiskManagerFileInfoListener, DownloadManagerPeerListener, PieceRTAProvider {
    private static int DEFAULT_BUFFER_MILLIS;
    private static int DEFAULT_MIN_PIECES_TO_BUFFER;

    static {
        COConfigurationManager.addAndFireParameterListeners(new String[] { "filechannel.rt.buffer.millis", "filechannel.rt.buffer.pieces", },
                new ParameterListener() {
                    public void parameterChanged(String parameterName) {
                        DEFAULT_BUFFER_MILLIS = COConfigurationManager.getIntParameter("filechannel.rt.buffer.millis");
                        DEFAULT_MIN_PIECES_TO_BUFFER = COConfigurationManager.getIntParameter("filechannel.rt.buffer.pieces");
                    }
                });
    }

    private static final boolean TRACE = false;

    private static final int COMPACT_DELAY = 32;

    private static final int MAX_READ_CHUNK_DEFAULT = 64 * 1024;

    private static final Comparator<dataEntry> comparator = new Comparator<dataEntry>() {
        public int compare(dataEntry o1, dataEntry o2) {
            long offset1 = o1.getOffset();
            long length1 = o1.getLength();

            long offset2 = o2.getOffset();
            long length2 = o2.getLength();

            long res;

            if (offset1 == offset2) {

                res = length1 - length2;

            } else {

                res = offset1 - offset2;
            }

            if (res == 0) {
                return (0);
            } else if (res < 0) {
                return (-1);
            } else {
                return (1);
            }
        }
    };

    private static final String channel_key = "DiskManagerChannel";
    private static int channel_id_next;

    // hack to allow other components to be informed when channels are created

    private static CopyOnWriteList<channelCreateListener> listeners = new CopyOnWriteList<channelCreateListener>();

    public static void addListener(channelCreateListener l) {
        listeners.add(l);
    }

    public static void removeListener(channelCreateListener l) {
        listeners.remove(l);
    }

    protected static void reportCreated(DiskManagerChannel channel) {
        Iterator<channelCreateListener> it = listeners.iterator();

        while (it.hasNext()) {

            try {
                it.next().channelCreated(channel);

            } catch (Throwable e) {

                Debug.printStackTrace(e);
            }
        }
    }

    public static interface channelCreateListener {
        public void channelCreated(DiskManagerChannel channel);
    }

    private DownloadImpl download;

    private org.gudy.azureus2.pluginsimpl.local.disk.DiskManagerFileInfoImpl plugin_file;
    private org.gudy.azureus2.core3.disk.DiskManagerFileInfo core_file;

    private Set<dataEntry> data_written = new TreeSet<dataEntry>(comparator);

    private int compact_delay = COMPACT_DELAY;

    private List<AESemaphore> waiters = new ArrayList<AESemaphore>();

    private long file_offset_in_torrent;
    private long piece_size;

    private Average byte_rate = Average.getInstance(1000, 20);

    private long start_position;
    private long start_time;

    private volatile long current_position;

    private request current_request;

    private long buffer_millis_override;
    private long buffer_delay_millis;

    private PEPeerManager peer_manager;

    private long[] rtas;

    private int channel_id;

    private volatile boolean destroyed;

    protected DiskManagerChannelImpl(DownloadImpl _download, org.gudy.azureus2.pluginsimpl.local.disk.DiskManagerFileInfoImpl _plugin_file)

    throws DownloadException {
        download = _download;
        plugin_file = _plugin_file;

        core_file = plugin_file.getCore();

        DownloadManager core_download = core_file.getDownloadManager();

        if (core_download.getTorrent() == null) {

            throw (new DownloadException("Torrent invalid"));
        }

        if (core_download.isDestroyed()) {

            Debug.out("Download has been removed");

            throw (new DownloadException("Download has been removed"));
        }

        synchronized (DiskManagerChannelImpl.class) {

            channel_id = channel_id_next++;
        }

        TOTorrentFile tf = core_file.getTorrentFile();

        TOTorrent torrent = tf.getTorrent();

        TOTorrentFile[] tfs = torrent.getFiles();

        rtas = new long[torrent.getNumberOfPieces()];

        core_download.addPeerListener(this);

        for (int i = 0; i < core_file.getIndex(); i++) {

            file_offset_in_torrent += tfs[i].getLength();
        }

        piece_size = tf.getTorrent().getPieceLength();

        core_file.addListener(this);

        reportCreated(this);
    }

    public DiskManagerFileInfo getFile() {
        return (plugin_file);
    }

    public DiskManagerRequest createRequest() {
        if (core_file.getDownloaded() != core_file.getLength()) {

            boolean is_paused = download.isPaused();

            if (core_file.isSkipped() && !is_paused) {

                // don't mess with skipped state if paused

                core_file.setSkipped(false);
            }

            boolean force_start = download.isForceStart();

            if (!force_start) {

                // don't auto-start a paused torrent - the fact that it isn't running will be picked
                // up later when the requests blocks on data and the download is found to not
                // be running

                if (!is_paused) {

                    synchronized (download) {

                        Map dl_state = (Map) download.getDownload().getData(channel_key);

                        if (dl_state == null) {

                            dl_state = new HashMap();

                            download.getDownload().setData(channel_key, dl_state);
                        }

                        dl_state.put("" + channel_id, "");
                    }

                    download.setForceStart(true);
                }
            }
        }

        current_request = new request();

        return (current_request);
    }

    public long getPosition() {
        return (current_position);
    }

    public boolean isDestroyed() {
        return (destroyed);
    }

    public void dataWritten(long offset, long length) {
        if (TRACE) {
            System.out.println("data written:" + offset + "/" + length);
        }

        dataEntry entry = new dataEntry(offset, length);

        synchronized (data_written) {

            data_written.add(entry);

            compact_delay--;

            if (compact_delay == 0) {

                compact_delay = COMPACT_DELAY;

                Iterator<dataEntry> it = data_written.iterator();

                dataEntry prev_e = null;

                while (it.hasNext()) {

                    dataEntry this_e = it.next();

                    if (prev_e == null) {

                        prev_e = this_e;

                    } else {

                        long prev_offset = prev_e.getOffset();
                        long prev_length = prev_e.getLength();
                        long this_offset = this_e.getOffset();
                        long this_length = this_e.getLength();

                        if (this_offset <= prev_offset + prev_length) {

                            if (TRACE) {
                                System.out.println("merging: " + prev_e.getString() + "/" + this_e.getString());
                            }

                            it.remove();

                            prev_e.setLength(Math.max(prev_offset + prev_length, this_offset + this_length) - prev_offset);

                            if (TRACE) {
                                System.out.println("    -> " + prev_e.getString());
                            }

                        } else {

                            prev_e = this_e;
                        }
                    }
                }
            }

            for (int i = 0; i < waiters.size(); i++) {

                waiters.get(i).release();
            }
        }
    }

    public void dataChecked(long offset, long length) {
        // System.out.println( "data checked:" + offset + "/" + length );
    }

    public void peerManagerWillBeAdded(PEPeerManager manager) {
    }

    public void peerManagerAdded(PEPeerManager manager) {
        peer_manager = manager;

        manager.getPiecePicker().addRTAProvider(this);
    }

    public void peerManagerRemoved(PEPeerManager manager) {
        peer_manager = null;

        manager.getPiecePicker().removeRTAProvider(this);
    }

    public void peerAdded(PEPeer peer) {
    }

    public void peerRemoved(PEPeer peer) {
    }

    public long[] updateRTAs(PiecePicker picker) {
        long overall_pos = current_position + file_offset_in_torrent;

        int first_piece = (int) (overall_pos / piece_size);

        long rate = byte_rate.getAverage();

        int buffer_millis = (int) (buffer_millis_override == 0 ? DEFAULT_BUFFER_MILLIS : buffer_millis_override);

        long buffer_bytes = (buffer_millis * rate) / 1000;

        int pieces_to_buffer = (int) (buffer_bytes / piece_size);

        if (pieces_to_buffer < 1) {

            pieces_to_buffer = 1;
        }

        int millis_per_piece = buffer_millis / pieces_to_buffer;

        if (pieces_to_buffer < DEFAULT_MIN_PIECES_TO_BUFFER) {

            pieces_to_buffer = DEFAULT_MIN_PIECES_TO_BUFFER;
        }

        // System.out.println( "rate = " + rate + ", buffer_bytes = " + buffer_bytes + ", pieces = " + pieces_to_buffer + ", millis_per_piece = " +
        // millis_per_piece );

        Arrays.fill(rtas, 0);

        long now = SystemTime.getCurrentTime();

        now += buffer_delay_millis;

        for (int i = first_piece; i < first_piece + pieces_to_buffer && i < rtas.length; i++) {

            rtas[i] = now + ((i - first_piece) * millis_per_piece);
        }

        return (rtas);
    }

    public long getStartTime() {
        return (start_time);
    }

    public long getStartPosition() {
        return (file_offset_in_torrent + start_position);
    }

    public long getCurrentPosition() {
        return (file_offset_in_torrent + current_position);
    }

    public long getBlockingPosition() {
        request r = current_request;

        if (r == null) {

            return (file_offset_in_torrent + current_position);
        }

        return (file_offset_in_torrent + current_position + r.getAvailableBytes());
    }

    public void setBufferMillis(long millis, long delay_millis) {
        buffer_millis_override = millis;
        buffer_delay_millis = delay_millis;
    }

    public String getUserAgent() {
        request r = current_request;

        if (r == null) {

            return (null);
        }

        return (r.getUserAgent());
    }

    public void destroy() {
        destroyed = true;

        core_file.removeListener(this);

        core_file.getDownloadManager().removePeerListener(this);

        core_file.close();

        if (peer_manager != null) {

            peer_manager.getPiecePicker().removeRTAProvider(this);
        }

        boolean stop_force_start = false;

        synchronized (download) {

            Map dl_state = (Map) download.getDownload().getData(channel_key);

            if (dl_state != null) {

                dl_state.remove("" + channel_id);

                if (dl_state.size() == 0) {

                    stop_force_start = true;
                }
            }
        }

        if (stop_force_start) {

            download.setForceStart(false);
        }
    }

    protected class request implements DiskManagerRequest {
        private int request_type;
        private long request_offset;
        private long request_length;
        private List<DiskManagerListener> listeners = new ArrayList<DiskManagerListener>();

        private String user_agent;

        private int max_read_chunk = MAX_READ_CHUNK_DEFAULT;

        private volatile boolean cancelled;

        AESemaphore wait_sem = new AESemaphore("DiskManagerChannelImpl:wait");

        protected request() {
            start_time = SystemTime.getCurrentTime();
        }

        public void setType(int _type) {
            request_type = _type;
        }

        public void setOffset(long _offset) {
            request_offset = _offset;
            start_position = request_offset;
        }

        public void setLength(long _length) {
            if (_length < 0) {

                throw (new RuntimeException("Illegal argument"));
            }

            request_length = _length;
        }

        public void setMaximumReadChunkSize(int size) {
            max_read_chunk = size;
        }

        public long getRemaining() {
            synchronized (data_written) {

                return (request_length - (current_position - request_offset));
            }
        }

        public void setUserAgent(String str) {
            user_agent = str;
        }

        protected String getUserAgent() {
            return (user_agent);
        }

        public long getAvailableBytes() {
            if (plugin_file.getDownloaded() == plugin_file.getLength()) {

                return (getRemaining());
            }

            int download_state = download.getState();

            // if the file is incomplete and the download isn't running then we don't have a view
            // of what's available or not (to do this we'd need to add stuff to access resume data)

            if (download_state != Download.ST_DOWNLOADING && download_state != Download.ST_SEEDING) {

                return (-1);
            }

            synchronized (data_written) {

                Iterator<dataEntry> it = data_written.iterator();

                // may not have been compacted to we need to aggregate contigous entry lengths

                dataEntry last_entry = null;

                while (it.hasNext()) {

                    dataEntry entry = it.next();

                    long entry_offset = entry.getOffset();
                    long entry_length = entry.getLength();

                    if (last_entry == null) {

                        if (entry_offset > current_position) {

                            break;
                        }

                        if (entry_offset <= current_position && current_position < entry_offset + entry_length) {

                            last_entry = entry;
                        }
                    } else {

                        if (last_entry.getOffset() + last_entry.getLength() == entry.getOffset()) {

                            last_entry = entry;

                        } else {

                            break;
                        }
                    }
                }

                if (last_entry == null) {

                    return (0);

                } else {

                    return (last_entry.getOffset() + last_entry.getLength() - current_position);
                }
            }
        }

        public void run() {
            long rem = request_length;

            long pos = request_offset;

            long download_not_running_time = 0;

            try {

                while (rem > 0 && !cancelled) {

                    long len = 0;

                    synchronized (data_written) {

                        current_position = pos;

                        Iterator<dataEntry> it = data_written.iterator();

                        while (it.hasNext()) {

                            dataEntry entry = it.next();

                            long entry_offset = entry.getOffset();

                            if (entry_offset > pos) {

                                break;
                            }

                            long entry_length = entry.getLength();

                            long available = entry_offset + entry_length - pos;

                            if (available > 0) {

                                len = available;

                                break;
                            }
                        }
                    }

                    if (len > 0) {

                        if (len > rem) {

                            len = rem;
                        }

                        if (len > max_read_chunk) {

                            len = max_read_chunk;
                        }

                        DirectByteBuffer buffer = core_file.read(pos, (int) len);

                        inform(new event(new PooledByteBufferImpl(buffer), pos, (int) len));

                        pos += len;

                        rem -= len;

                        synchronized (data_written) {

                            byte_rate.addValue(len);

                            current_position = pos;
                        }
                    } else {

                        inform(new event(pos));

                        synchronized (data_written) {

                            waiters.add(wait_sem);
                        }

                        try {

                            while (true && !cancelled) {

                                if (wait_sem.reserve(500)) {

                                    break;
                                }

                                DownloadManager dm = core_file.getDownloadManager();

                                if (dm.isDestroyed()) {

                                    throw (new Exception("Download has been removed"));

                                } else if (core_file.isSkipped()) {

                                    throw (new Exception("File is 'do not download'"));

                                } else {

                                    int state = dm.getState();

                                    if (state == DownloadManager.STATE_ERROR || state == DownloadManager.STATE_STOPPED) {

                                        long now = SystemTime.getMonotonousTime();

                                        if (download_not_running_time == 0) {

                                            download_not_running_time = now;

                                        } else if (now - download_not_running_time > 15 * 1000) {

                                            if (dm.isPaused()) {

                                                throw (new Exception("Download has been paused"));

                                            } else {

                                                throw (new Exception("Download has been stopped"));
                                            }
                                        }
                                    } else {

                                        download_not_running_time = 0;
                                    }
                                }
                            }
                        } finally {

                            synchronized (data_written) {

                                waiters.remove(wait_sem);
                            }
                        }
                    }
                }
            } catch (Throwable e) {

                inform(e);
            }
        }

        public void cancel() {
            cancelled = true;

            inform(new Throwable("Request cancelled"));

            wait_sem.release();
        }

        protected void inform(Throwable e) {
            inform(new event(e));
        }

        protected void inform(event ev) {
            for (int i = 0; i < listeners.size(); i++) {

                try {
                    ((DiskManagerListener) listeners.get(i)).eventOccurred(ev);

                } catch (Throwable e) {

                    Debug.printStackTrace(e);
                }
            }
        }

        public void addListener(DiskManagerListener listener) {
            listeners.add(listener);
        }

        public void removeListener(DiskManagerListener listener) {
            listeners.remove(listener);
        }

        protected class event implements DiskManagerEvent {
            private int event_type;
            private Throwable error;
            private PooledByteBuffer buffer;
            private long event_offset;
            private int event_length;

            protected event(Throwable _error) {
                event_type = DiskManagerEvent.EVENT_TYPE_FAILED;
                error = _error;
            }

            protected event(long _offset) {
                event_type = DiskManagerEvent.EVENT_TYPE_BLOCKED;

                event_offset = _offset;
            }

            protected event(PooledByteBuffer _buffer, long _offset, int _length) {
                event_type = DiskManagerEvent.EVENT_TYPE_SUCCESS;
                buffer = _buffer;
                event_offset = _offset;
                event_length = _length;
            }

            public int getType() {
                return (event_type);
            }

            public DiskManagerRequest getRequest() {
                return (request.this);
            }

            public long getOffset() {
                return (event_offset);
            }

            public int getLength() {
                return (event_length);
            }

            public PooledByteBuffer getBuffer() {
                return (buffer);
            }

            public Throwable getFailure() {
                return (error);
            }
        }
    }

    protected static class dataEntry {
        private long offset;
        private long length;

        protected dataEntry(long _offset, long _length) {
            offset = _offset;
            length = _length;
        }

        protected long getOffset() {
            return (offset);
        }

        protected long getLength() {
            return (length);
        }

        protected void setLength(long _length) {
            length = _length;
        }

        protected String getString() {
            return ("offset=" + offset + ",length=" + length);
        }
    }
}
